This invention relates in general to the field of optical films and, more particularly, to a method and apparatus for trimming a pellicle film using a laser.
Photomasks, commonly referred to as xe2x80x9cmasksxe2x80x9d or reticles, are used in the manufacture of semiconductor integrated circuits (ICs). Photomask are typically made of a transparent substrate on which an opaque patterned layer has been applied. By exposing the photomask to a particular wavelength of light, an image is projected through the photomask onto a semiconductor wafer causing an imprint of the patterned layer on the wafer.
Because a photomask is used to project this image, any defect on the surface of the photomask will result in a transferred imperfection onto the wafer, possibly rendering it useless. Therefore, manufacturers of semiconductor ICs take great care to protect the quality of photomasks used in the manufacturing process. To further protect such photomask quality, pellicles have been developed.
A pellicle protects the quality of an image plane on a photomask by preventing contaminants from collecting in the image plane of the patterned layer that is to be transferred to the wafer. Traditionally, the pellicle is formed by adhering a thin polymer film to a metal or plastic frame. When gluing the film to the frame, the film typically contains an excess portion that extends beyond the edges of the frame. Currently, the excess portion is trimmed by hand with a surgical scalpel blade. Because this mechanical process of cutting the film causes particulate matter, a swabbing step is included to prevent small particles from contaminating the pellicle. A typical swabbing step includes a foam swab wetted with a solvent for removing particles from the trimmed edge and sealing the trimmed edge to the frame. The removal of the particulate matter prevents pellicle contamination and possible rejection of the pellicle for use in the manufacture of semiconductor ICs.
A potential for particulate matter contamination further exists in shipping of a trimmed pellicle. The trimmed pellicle may still contain portions of the pellicle film that extend beyond a pellicle edge when placed into a shipping container. The trimmed edge may come into contact with the shipping container and cause particles to break off, which may further contaminate the pellicle.
In accordance with the teachings of the present invention, disadvantages and problems associated with a method and apparatus for trimming a pellicle film using a laser have been substantially reduced or eliminated. In particular embodiment, a laser trimming assembly includes a hose port that removes particulate matter from a pellicle during a trimming process.
In one embodiment of the present invention, a laser trimming assembly includes a modified laser-cutting head coupled to a laser. The laser includes a laser beam for trimming a pellicle film that extends beyond a perimeter of a pellicle frame. The modified laser-cutting head includes a nozzle and at least one hose port located on the nozzle. The hose port may receive a vacuum hose that removes particulate matter created during a trimming process.
In another embodiment of the present invention, a method for trimming a pellicle film using a laser includes aligning a laser trimming assembly over a portion of a pellicle film that extends beyond a pellicle frame on a pellicle assembly. The laser trimming assembly uses a laser to trim the pellicle film while following the perimeter of the pellicle frame. During the trimming process, a vacuum source removes particulate matter created during the laser trimming process.
In a further embodiment of the present invention, a pellicle assembly includes a pellicle film coupled to a pellicle frame. A damage resistant film edge is formed on the pellicle frame by removing the pellicle film from over an outer edge of the pellicle frame.
In an additional embodiment of the present invention, a photomask assembly includes a pellicle assembly coupled to a photomask. The pellicle assembly includes pellicle film coupled to a pellicle frame. A damage resistant film edge is formed on the pellicle frame by removing the pellicle film from over an outer edge of the pellicle frame.
Important technical advantages of the present invention include a technique for trimming the pellicle film that removes particulate matter created during the trimming process. In one embodiment, a vacuum hose connects to a nozzle located on a laser trimming assembly. The vacuum hose removes any particulate matter that is released during the trimming process to prevent contaminants from settling on the pellicle assembly.
Another important technical advantage of the present invention includes a laser trimming technique that reduces the time required to trim a pellicle film. Conventional trimming methods often require a technician to trim the edges by hand with a surgical scalpel. Thus, the trimming time is limited by how fast each individual can perform the procedure. Because the laser trimming assembly may be computer controlled, the trimming process may be performed faster and with a greater precision and accuracy than the hand trimming process.
A further important technical advantage of the present invention includes a laser trimming technique that creates a recessed film edge, which eliminates contact between a pellicle film edge and a pellicle assembly shipping box. If any excess portion of a pellicle film extends beyond the edges of a pellicle frame, the excess portion may come in contact with the pellicle assembly shipping box and produce abraded particles. These particles may further contaminate the surface of the pellicle film. By providing a recessed edge, the edge of the pellicle film will generally not come in contact with the pellicle assembly shipping box, thus reducing the possibility of producing extra contaminants on the pellicle assembly surface.
All, some or none of these technical advantages may be present in various embodiments of the present invention. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.